OsmoBSC: update VTY reference

This is the first update since the libosmocore changes to the 'show
online-help' generated output. Hence the produced document now benefits from
the structural improvements:
- not repeating common commands for every node;
- using section names that match the VTY prompt.

Update bsc_vty_additions.xml to match the new node ID scheme.

Change-Id: I0d856563eee88527fda4c6940aa6cea779175aaa

doc/manuals/vty/bsc_vty_additions.xml

@@ -1,13 +1,9 @@
 <vtydoc xmlns='urn:osmocom:xml:libosmocore:vty:doc:1.0'>
-    <node id='25'>
-      <child_of nodeid='4' />
-      <name>MSC Connection Commands</name>
+    <node id='config-msc'>
       <description>This node allows to configure the MSC connection related
       settings.</description>
     </node>
-    <node id='30'>
-      <child_of nodeid='4' />
-      <name>BSC Commands</name>
+    <node id='config-bsc'>
       <description>This node allows to configure the BSC connection related
       settings.</description>
     </node>